The importance of developing more effective treatments for obsessive compulsive disorder (OCD) is underscored by recent epidemiological data suggesting that previious studies may have underestimated the prevalence of OCD in the general population by as much as 20-fold. The life time prevalence for the disorder is between 2 and 3%. Children and adolescents are frequently affected by OCD: nearly 80% of adult patients have their onset in childhood or adolescence. The key clinical features of OCD are strikingly similar between children, adolescents and adults. These features consist of recurrent obsessional thoughts or impulses, and/or repetitive, purposeful and intentional (i.e., compulsive) behaviours that are performed in response to an obsession or certain rules. The obsessions & compulsions cause marked distress, are time consuming or significantly interfere with the youngster;s normal routine, school functioning or usual social activities or relationships. Phase I of this study is a 16 week,open label phase. Phase II is a 16 week double-blind discontinuation phase followed by a 6 week double-blind down titration.